645845 has 4 divisors (see below), whose sum is σ = 775020. Its totient is φ = 516672.

The previous prime is 645839. The next prime is 645851. The reversal of 645845 is 548546.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (645839) and next prime (645851).

It can be written as a sum of positive squares in 2 ways, for example, as 130321 + 515524 = 361^2 + 718^2 .

It is a cyclic number.

It is not a de Polignac number, because 645845 - 2¹² = 641749 is a prime.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 64580 + ... + 64589.

It is an arithmetic number, because the mean of its divisors is an integer number (193755).

2⁶⁴⁵⁸⁴⁵ is an apocalyptic number.

It is an amenable number.

645845 is a deficient number, since it is larger than the sum of its proper divisors (129175).

645845 is a wasteful number, since it uses less digits than its factorization.

645845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129174.

The product of its digits is 19200, while the sum is 32.

The square root of 645845 is about 803.6448220452. The cubic root of 645845 is about 86.4389402803.

The spelling of 645845 in words is "six hundred forty-five thousand, eight hundred forty-five".